<!DOCTYPE html>

<div style="position:absolute; left:50px;">
    <div style="position:absolute; top:50px; transform-style:preserve-3d;">
        <div style="position:fixed; left:5px; top:5px; width:50px; height:50px; background-color:green;">
        </div>
    </div>
</div>


<div style="position:absolute; left:50px;">
    <div style="position:absolute; top:150px; perspective:1px;">
        <div style="position:fixed; left:5px; top:5px; width:50px; height:50px; background-color:green;">
        </div>
    </div>
</div>
